Injuries in recreational endurance runningStudies completed in 1998 in endurance athletes, estimated overuse injuries have been estimated to cause between 35%-65% of all sports injuries 1. As we can see in the City to Surf, with a record number of participants in 2007B, there is an ever-increasing number of ‘fun-run’ participants since these figures were released, increasing the need for safe and effective training programs for all levels of participants. As we see an exponential increase in the number of participants in these endurance ‘fun runs’ there is also an increase in injuries due to poor technique, preparation, core strength and footwear. This document discusses the main fibre characteristics of an endurance runner, effective training methods, how injuries may occur and how they could be avoided. Main fibre characteristics of the athlete and why Endurance athletes predominantly engage slow-twitch muscle fibres, which take approximately 110ms to reach peak tension as opposed to fast twitch, which take approximately 50ms3 . Some studies indicate that the predominant muscle fibre type in any individual is determined earlier in life, based on environment, genetics and activity patterns. Whilst other studies suggest that muscle fibres can, to a certain extent, be cultivated dependant on the activity pattern and training program3. The nature of endurance sport such as marathons, triathlons, ironman and other long-distance events requires longer, sustained movement as opposed to the short bursts provided by Fast Twitch, so there is a requirement for efficient production of ATP. Slow Twitch fibres have a higher level of aerobic endurance meaning oxidation, so are recruited in low-intensity endurance events and are therefore very efficient at producing ATP from the oxidation of Carbohydrate and Fat3. World champions in the marathon have been reported to possess 93% – 99% Slow Twitch fibres in their gastrocnemius muscles, whilst sprinters have been reported to only have 25% Slow Twitch fibres3. In addition, Slow Twitch fibres have been seen to have a higher level of lactate dehydrogenase than Fast Twitch fibres, post-exercise, with one study indicating that this is caused by an “increase in muscle cell membrane permeability which occurs as the cell becomes energy depleted… with elevated levels of this enzyme following endurance training”4 . Training to optimise Slow Twitch fibres When training to optimise slow twitch fibres it is important to consider the fibres use of oxygen, the V02 of the muscle fibres vs exertion levels to ensure the aerobic pathway to ATP production, allowing sustained exercise for the endurance athlete. Thresholds exist where the muscle fibre will commence on the anaerobic pathway, depending on the availability of oxygen, engaging Fast Twitch fibres and limiting the capacity of the muscle to perform sustained endurance movement. Hence, endurance athletes should employ methods of determining their individual aerobics threshold, some use perceived exertion tests such as the ability of talking during exercise. Additionally a steady increase in distance and length of training will allow the muscle fibre to adapt and become more efficient in its use of oxygen to create ATP. Intrinsic/ Extrinsic factors causing injury Intrinsic Biomechanics The simple mismatch between stress on any given tissue and the ability of that tissue - regardless whether it’s bone, soft, tendon or cartilage – to withstand the stress, is the main principal behind biomechanical overuse injuries. Eg, stress fractures occur when forces exceed the ability of the bone to ‘remodel’5. Overtraining A common factor in causing injury is overtraining, which manifests in a range of symptoms. Whilst the musculoskeletal system is extremely adaptable, finding the correct balance between maximizing a training response and avoiding overtraining can be difficult. According to Ball’s 2010 paper on training overload and the adaptiveness of the musculoskeletal system “Overtraining can occur because of musculoskeletal imbalances, poor muscular coordination, inadequate skill, inappropriate training, fatigue and incomplete rehabilitation from a previous injury” 6. Physiological structure Additionally there may be structural biomechanics affecting the ability to perform and withstand injury, eg ‘bow’ legs inherited in an individual. This is purely based on chance and genetics and can inhibit the limbs ability to be active at a functional range-of-movement for optimal performance. technique and posture Effective sustained movement for endurance athletes requires optimal posture and strength. Whilst the importance of core strength is often debated, it is essential that the body can maintain this posture, past the point of muscle fatigue. Eg, rounded shoulders in a marathon runner will limit the level of power exerted from the upper body in maintaining movement and can result in quicker muscle fatigue of smaller ‘stabiliser’ muscles. A 2009 study7 demonstrated that pectoralis minor muscle tension resulted in reduced lower trapezius strength, which was improved through pectoralis minor soft tissue mobilization and self-stretching.
Extrinsic Training Increased training stimulus - increasing duration, frequency and mileage - can result in maladaptation due to exposure to a stimulus too frequently or a stimulus that involves forces that are beyond the capability of the musculotendinous system. As the body struggles to adapt and keep up with the additional force caused by increased training programs, further strain is placed on tissue.
Equipment A very common cause of injury is poor or incorrect footwear. With the broad range of choice in terms of running footwear, novices often make incorrect choices based on aesthetics as opposed to biomechanics. Andrew Bull of Sydney Sports Podiatry often lectures at Nike and Footlocker staff forums to promote the importance of correct footwear in endurance sports. “The wrong pair can exacerbate a problem. If you’re an over-pronator in a soft shoe, it can make your arches collapse further. Alternately, if a person who doesn’t roll enough wears a heavy, motion- control shoe, they’ll supinate, which can lead to stress fractures,” cautions Bull. Environment Training on uneven terrain can affect the instance of injury due to increased chance of ‘rolling’ at the joints as well as the bodies inability to adapt to the ever-changing medial gradients. Additionally, training on either hard or soft terrains will place varying impact on the musculoskeletal system, which can ultimately increase exterted force on these structures. Main overuse injuries sustained by the athlete There are some common injuries sustained by the recreational runner as a result of overuse, including:
Stress fractures Stress fractures are most commonly seen in the lower extremities, particularly in the Tibia, although they can also occur in the foot and ankle, as well as occasionally in the Femur 1. Tendonitis Whilst tendonitis is not limited to the lower limb, Achilles tendonitis is the most common form of tedinopathy. Achilles tendonopathy is a recognised complication of running activities. As outlined above, aetiological factors include running surfaces, poor flexibility and strength, partially worn out shoes, training errors and lower limb biomechanical factors. This can be a slow degenerative condition that if left undiagnosed can lead to subcutaneous rupture. It is also common to see knee related tendonitis, with meniscus injuries often requiring surgery. A study on recreational runners concluded that patellofemoral pain syndrome could act as a precursor to tendon damage 8. Muscle tears Alongside tendon injuries, muscle tears are a common injury factor in recreational runners. Largely due to poor preparation or ‘too much too soon’ muscle tears are a result of excessive force on the muscle fibre, past its point or ability to adapt. Muscle tears can also be a result of inflexible, tight muscle and poor stretching techniques. One form of prevention commonly implemented is the use of Proprioreceptive Neuromuscular Facilitation (PNF) stretching. A 2004 study concluded that the use of contract-relax PNF stretching saw significant improvement on hamstring flexibility from the control group, which incorporated no stretching9. This increase in flexibility was considered to be a “valuable component of athletic performance and injury reduction”9.
Sprains
Ankle sprains are the most common of this type of injury with recreational runners experiencing ‘rolled’ ankles from joint instability, poor footwear or uneven surfaces. Acute ankle sprains have been reported to comprise of approximately 12% of all injuries seen in emergency rooms and 15% of athletic injuries10 . This is an acute injury that is most common laterally. Following ankle sprain runners may experience peroneal muscle weakness, resulting in the facilitation of the soleus, peroneus longus and tibial is anterior to stabilise the joint and maintain posture and movement. Massage as a treatment As a form of prevention as well as injury treatment, massage is able to increase range-of-motion around the joint by releasing and stretching soft tissue. The biomechanical processes involved in recreational running, as outlined above often cause reduction in mobility which can have a longer term impact on the joints. Massage also increases circulation, aiding muscle recovery and increase of nutrients oxygen to areas of injury or inflammation. In addition to this, the use of massage enables sedation of the sympathetic nervous system allowing the body to relax and release muscle tension, thereby avoiding further injury or strain. Conclusion With ever increasing obesity levels it is encouraging to see the number of recreational running participants growing however it is also increasingly important to ensure that effective training and preparation methods are passed on to all levels to avoid serious musculoskeletal and ligament damage further down the track. Correct training techniques are no longer simply available for elite athletes, with information becoming more widespread through event organisers and sports practitioners. With this in mind we hope to see a long-term reduction in injuries and even more increase in the enjoyment of endurance sports.
4.Rumley A. G., Pettigrew A. R. , Colgan M. E., Taylor R., Grant S., Manzie A., “Serum Lactate Dehydrogenase and Creatine Kinase during marathon training” Journal of Sports Medicine, 1985, p161.
Bibliography Andrew Bull, Sydney Sports Podiatry, 9-13 Young Street Sydney.
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